https://en.wikipedia.org/wiki/Gunnora

About Gunnor, Duchess of Normandy
Parents unknown, but often pretended to be a fictitious Herbastus de Crepon. See Todd A. Farmerie, Robert de Torigny and the family of Gunnor, Duchess of Normandy .

According to Robert de Torigny, she was a virgin living with her married sister Senfrie when Duke Richard of Normandy became enamored of Senfrie. Senfrie managed to substitute Gunnora, who became mistress, and later wife, of Duke Richard of Normandy. Gunnora then used her influence to arrange good marriages for her sisters Wevia and Aveline and for her nieces whom he leaves unnamed.

Richard and Gunnora were parents to several children:

Richard II "the Good", Duke of Normandy[15]
Robert, Archbishop of Rouen, Count of Evreux, died 1037[15]
Mauger, Count of Corbeil[15]
Emma of Normandy , married first to Æthelred, King of England and secondly Cnut the Great, King of England.[15]
Hawise of Normandy, wife of Geoffrey I, Duke of Brittany[15]
Maud of Normandy, wife of Odo II of Blois, Count of Blois, Champagne and Chartres[15]